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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.reference.is_constructible"></a><a class="link" href="is_constructible.html" title="is_constructible">is_constructible</a>
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<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">is_constructible</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span>
</pre>
<p>
        <span class="bold"><strong>Inherits:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
        can be constructed from <code class="computeroutput"><span class="identifier">Args</span></code>,
        then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
        otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
        Type <code class="computeroutput"><span class="identifier">T</span></code> must be a complete
        type.
      </p>
<p>
        Formally the trait answers the question, is the expression:
      </p>
<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">declval</span><span class="special">&lt;</span><span class="identifier">Args</span><span class="special">&gt;()...);</span>
</pre>
<p>
        valid?
      </p>
<p>
        There are a number of important special cases for this trait:
      </p>
<pre class="programlisting"><span class="identifier">is_constructible</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span>
</pre>
<p>
        Indicates whether <code class="computeroutput"><span class="identifier">T</span></code> is default
        constructible, while:
      </p>
<pre class="programlisting"><span class="identifier">is_constructible</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&amp;&gt;::</span><span class="identifier">value</span>
</pre>
<p>
        Indicates whether <code class="computeroutput"><span class="identifier">T</span></code> is copy-constructible,
        and:
      </p>
<pre class="programlisting"><span class="identifier">is_constructible</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span>
</pre>
<p>
        Indicates whether <code class="computeroutput"><span class="identifier">T</span></code> is move-constructible.
      </p>
<p>
        <span class="bold"><strong>Compiler Compatibility:</strong></span> This trait requires
        the C++11 features <code class="computeroutput"><span class="keyword">decltype</span></code>
        variadic templates and SFINAE-expression support for full support. While
        there is some fallback code for cases where this is not the case, the trait
        should really be considered broken in that case. The header will define the
        macro <code class="computeroutput"><span class="identifier">BOOST_TT_IS_CONSTRUCTIBLE_CONFORMING</span></code>
        when the full implementation is available.
      </p>
<p>
        <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
        <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">is_constructible</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
      </p>
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        Distributed under the Boost Software License, Version 1.0. (See accompanying
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